Wednesday, October 4, 2017

Research @ Otago - Rebecca McMullin


Rebecca’s research focuses on tracking the flow and fate of waste materials from salmon farms through food webs in the Marlborough Sounds.
Salmon aquaculture involves the input of large quantities of feed into sea farms, which in turn results in the production of organic and nutrient wastes that have the effect of increasing the ecological footprints of the farm. This may have consequences for the connectivity of food webs within the farm's ecological footprint.
Bagging and labelling samples

With help from a team of researchers in the Department of Marine Science, Rebecca has collected key species of fish, macroinvertebrates and benthic infauna (small invertebrates that live in the sediment) from around salmon farms in the Marlborough Sounds. These samples are now being processed and analysed to determine the proportion of organic matter each organism sources from farm waste relative to the proportion they source from natural marine sources such as macroalgae and phytoplankton.

Collecting samples from a salmon farm in the Marlborough Sounds

Rebecca has also set up mesocosms (like miniature ecosystems) at Portobello Marine Laboratory that will allow us to measure parameters that are useful for modelling the real-world system in the Marlborough Sounds. 
Mesocosm set up at the Portobello Marine Laboratory
Ultimately this research will be useful in minimising negative impacts of aquaculture on natural ecosystems.
 

Wednesday, September 6, 2017

Research @ Otago - Daniel Smart

Daniel’s research focuses on understanding one of the most pivotal aspects of an organism, its reproductive cycle, and how a warming ocean will affect the development of larvae. 


Daniel is working on the blue mussel (Mytilus galloprovincialis), a species in New Zealand for which there are large knowledge gaps. Trying to fill these knowledge gaps is of importance as blue mussels are significant organisms, having key roles in coastal marine ecosystems.
Daniel is investigating the timings of the reproductive cycle by taking monthly samples and looking at which stage they are at in their reproductive cycle. This will be carried out over a 12-month period, enabling an understanding of the timings of the reproductive cycle.   
Blue mussel open ready for dissection
Daniel is also looking at how blue mussel larvae will respond to a warming ocean, with experiments being run using different temperature treatments, and assessing the impacts of these different temperatures on the development and survival of the larvae.

Thursday, January 19, 2017

Research @ Otago - Nadjejda Espinel


Nadjejda is studying the effects of climate change on marine ecosystems, and marine invertebrates in particular.   

Nadjejda raises the microscopic larvae in the laboratory
Nadjejda's research focuses on the effects of ocean acidification and warming on the larval settlement of some New Zealand key species including paua, kina, barnacles (Austrominius modestus) and polychaetes (Galeolaria hystrix), trying to understand how these species will fare in future acidified and warmed-up oceans.
The approximate size of the Nauplius larvae is 0.5mm
Most of the sessile  (organisms that live attached to the substrate) and benthic marine invertebrates spawn planktonic larvae into the water column. These larvae swim freely until they find a place appropriate to spend their adult lives and then they settle and metamorphose - this is what we call the settlement process. Any factors influencing the settlement process might influence the future distribution of species and ultimately the diversity of the marine ecosystems.  The settlement process could be influenced by direct changes in the larval physiology, or by indirect changes in the settlement substrates.
Nadjejda collecting adult barnacles from the rocks at Portobello Marine Laboratory
In order to study this, Nadjejda collects invertebrates (adults), spawns them and rears the larvae in the lab, in order to get them to settle. The core of her research comprises experiments in the lab trying to settle larvae in different pH treatments on different types of substrates, in order to see whether a significant effect can be expected at the future predicted levels of acidification and warming.

Thursday, August 11, 2016

Research @ Otago - Rob Lewis

Rob is working on a system to identify individual Sevengill sharks so New Zealand's Sevengill shark populations can be catalogued for future study and analysis.


Many of our local species of sharks are lesser known or unheard of in New Zealand as is the case in the Sevengill shark (Notorynchus cepedianus).  Sevengill sharks are important coastal predators that help regulate the health our local marine ecosystems. There are, however, large gaps of knowledge pertaining to the basic parameters of Broadnose Sevengill population size, composition, life span, growth rates, sexual maturity and vulnerability to fishing pressures in New Zealand.



Through the use of baited underwater camera stations we can identify each individual Sevengill encountered and start getting to know some of these missing characteristics of the NZ population. Rob's study focuses on a population of Sevengill sharks in Paterson Inlet, Stewart Island, that exhibits an all-year-round presence. The use of baited remote video systems to sample this population is ideal as they are a non-invasive, repeatable, cost-effective and easy to deploy. 



Once there is a catalogue of individuals it will be possible to start characterising the Paterson Inlet population demographics including abundance, estimated population size, sex ratio, size ranges and maturity. Only with these data present and accurate can sensible and effective future management decisions be made regarding the species.

Sunday, April 17, 2016

Research @ Otago - Kate Sparks

Kate is studying Antarctic starfish - What can they tell us about how polar marine life may adapt to a warmer world?


The Antarctic seas are among the fastest warming and acidifying waters on the planet, and the animals living there need to adapt - or face becoming vulnerable to extinction. Antarctic sea stars, which are important 'keystone' species in their ecosystems, can tell us a lot about the responses of polar marine species to ocean warming and acidification.

Kate checking out the seastar specimens in the lab at Scott Base

Kate Sparks has been working with the Antarctic cushion star to characterise the adaptive capacity and genetic variation within the wild population in response to warmer and acidified conditions. This is an important step in understanding the potential consequences of global ocean change on marine life in Antarctica.

Penguins - although not the species studied by Kate, they are very photogenic!

Tuesday, September 8, 2015

Research @ Otago - Tyler Northern

Tyler is studying the mineral make up of statoliths (a hard structure that works as a gravity receptor) from warty squid (Onykia ingens).

I am working closely with a group at the ALCES lab at AUT run by Dr Kathrin Bolstad who also study cephalopods (squid and octopus) around NZ.  As a result, I have recently been on a trawl survey with NIWA on their research vessel, the Tangaroa. I spent three and a half weeks living aboard the Tangaroa on the Chatham Rise in August 2015 and my job was to identify and collect cephalopods.
The RV Tangaroa docked in Lyttleton, Christchurch (Photo: Nathania Brooke)

Being aboard the Tangaroa was an amazing experience, I met lots of really easy going people and we were fed very well! We were targeting mid-trophic level organisms which means we wanted to catch the things that big fish eat, although we did get a few big fish! We measured and weighed all of the fish we caught and took stomach and tissue samples from a sub-sample of them to be analysed at NIWA.
Tyler with a 18kg Ling caught and sampled on the Chatham Rise

We also caught a lot of cool squid including my study animal! 

A mature warty squid (Onykia ingens) hauled up from the depths

If you have any questions you can email me at: tyler.northern@otago.ac.nz

Wednesday, July 29, 2015

Research @ Otago - Sorrel O'Connell-Milne

Sorrel is studying how parasite infection in clams varies in a commercial harvested environment.

Sorrel's research looks at the number of parasitic infections in the clam Austrovenus stutchburyi in  areas where commercial harvesting takes place and compares these with areas where there has been no harvesting.  She also examines the effect of these parasites on juvenile clam mortality, growth, body condition and foot length.

Mud snails were collected from Otago Harbour and their parasites were used to experimentally infect the juvenile clams and observe changes in their growth, body condition and foot length.
The parasites she studies are Curtutaria australis and Acanthoparyphium spp., two trematodes that play very similar roles within the ecosystem. These trematodes have a complex life cycle and require three different host species before they can reach maturity. The first intermediate host is a gastropod (whelk or mud snail) where the parasite infects the gonadal material, castrating the host and effectively turning the host into a 'parasite factory'.  The parasite then infects the second intermediate host, the clam, where the inactive juvenile stage is encapsulated as a cyst in the clam's foot.  The oystercatcher is the definitive host for the parasite and the trematode’s life cycle is completed when the oystercatcher preys upon the clam and ingests the trematode.
The trematodes encyst within the foot of the clam where they reduced foot muscle contractions and hinder burrowing behaviour.
As these parasites infect the foot of the clam they reduce the ability of the clam to bury into the sediment, increasing the chance of predation by birds seven-fold.  Effectively, the trematode is changing the clams burrowing behaviour and actively enhancing its own transmission to the definitive host, the oystercatcher.  However, not all is doom and gloom, parasites also have effects on the surrounding infauna; the shells of clams held above the sediment provide attachment surfaces and shelter for other organisms, which can result in increased biodiversity of the area.

Sorrel and her field volunteers, Chris and Steph, collecting clams in Blueskin Bay, Otago.
Areas with a reduced density of shellfish due to commercial harvesting were found to have 36% more parasites on average than equivalent unharvested areas. Results indicate that although mortality was unaffected by parasites infection directly, increased infestations negatively affect the growth, body condition and foot length of clams.  Therefore, in harvested areas increasednumbers of infections may result in the clam reaching maturity later and their ability to filter feed and bury into the sediment may be reduced.  This study portrays the complex impacts that human activity may have on the intertidal environment and highlights that commercial clam harvesting not only removes shellfish biomass but also has more inconspicuous effects on the surrounding ecosystem.